My 248 LS is an '03 with the Mercury 350 Mag and Bravo 3 Sterndrive
I happened to meet another person over the summer who had a 248 LSC who had added tabs. They indicated it made a huge difference in performance, so I thought I would give them a shot. He had the same issues that I am having.
I can understand some "wandering", but what I get is excessive. Granted, I am not a seasoned boater (less than 3 yrs), but I have been on other boats that do not seem to have this issue.
Thanks for the post.